Oh dear, go have a rest now.
I know how you feel. I sometimes think about my grandma too. She's old and she's not as healthy as before. I can't imagine if she's not beside me anymore, I love her so much, she often cooks for me, gives me lot of stuffs, and she often asks me to stay with her in her house. Oh no, I think I can't cheer you up because I have the same problem :(
Take care :)

Sephine! D: You shouldn't be dealing with feelings like that! It's an awful thing to think things like that! I know, cause I do it all the time. I have so many different fears about when my grandparents die. See, I've never lived with my parents. They weren't able to take care of my sister and I, so my grandparents are like parents to me. If I lose them, I'll be devastated. My dad is in poor shape, between his fibromyalgia and his being so overweight. I worry for his life EVERY DAY. And him and I fight a lot, so I'm always afraid that we're going to have a huge fight, and then he's going to pass away, with us on such bad terms. I'd want to be able to tell him how much I appreciate and love him, of course. But I always fear that it won't happen that way.

I think it's natural for all for people to have fears about losing people close to them. And when you're exhausted, and under so much stress, the depressing thoughts like that are more likely to arise. I know because my thoughts like that happen mostly when I can't fall asleep at night, or if my brain is frying from stress.

I don't know what to tell you to help you keep your mind off it. All you can do is try to keep your head full of positive thoughts. After you rest, I bet you'll feel a bit better.

The best thing you can do is to make the most out of the time with them. Do things with them, take care of them and let them know how much you care, every single day. It will help.

You just have to be strong, and shove those horrible thoughts away. Talking to people always helps me, and talking about it in my world, like you're doing here. It's helped me so many times in the past. It's always good to know that you have friends who care about you, and who are willing to support you. And if anything were to happen to them, you can bet your ass I'll be here for you! I'm always here if you need to talk. I know what it's like to think things like that, and it makes you feel alone and depressed. ;-;

Cheer up girl! *huggles*

I'm really sorry to hear that about your grandparents! >_< Just don't dwell on negative possibilities, and enjoy the time that you have with them right now! Make the best of the time you spend together, and you will be a much happier person. :D

And get some sleep, girl!!

Aww, I am sorry to hear that... D: You shouldn't think too much. Just live and think on all nice things and don't think what will happen. YOU MUST NOT LET THOSE MEMORIES GET YOU!! Sorry, but I want to help that you actually don't feel sad. I can't do much though, but only to say that it is not as dark and that reality as it seems. Reality can be positive too, so see it in that way as well!